Aqueous fluids, including wastewater produced by industrial enterprises, such as factories, as well restaurants, households and from many other sources, are likely to contain pollutants, such as oils, e.g., mineral and vegetable oils, and crude oil, are often discharged into oceans, seas or rivers which may cause serious ecological problems. When the seas or rivers are polluted with large amounts of oils, the oils are generally enclosed by oil fences to prevent them from dispersing, and then are recovered. Further, the oils are often adsorbed, solidified and recovered by use of oil-gelling agents. However, if the rivers run fast or the oceans and seas are turbulent, e.g., because of high tides or extreme weather conditions, such as hurricanes, it is difficult to adsorb and solidify the oils. Accordingly, under such conditions, it may be difficult to contain and solidify the oils. As a result, oil slicks are formed which are washed up on the beaches and adversely affect seabirds and/or marine life.
On the other hand, in a water purification system for treating wastewater (such as industrial and domestic wastewaters) containing a small amount of oils dispersed therein, the wastewater is generally filtered through a filter to remove the oils. However, since the filter in the system has a tendency to clog with the oils, it is necessary to change the filter frequently. Hence, considerable cost and effort are required to maintain the system. Further, if the wastewater contains a large amount of oils, the oils and the water may separate to form upper and lower layers, respectively. If the wastewater containing such layers is filtered, the filter often clogs. To avoid the clogging it is necessary to perform time and effort consuming pretreatments of such wastewater. The pretreatments may include spreading, inorganic or organic adsorbents, such as silica and pearlite, or organic water purification agents comprising oleophilic polymers, on the wastewater before the filtration. However, it is difficult to collect and recover the organic adsorbents and polymers, and the inorganic adsorbents are generally poor in oil adsorbability.
JP-A 2000-176306 discusses a method of recovering oil floating on water surface. Heavy oil is recovered by dispersing a magnetic body and magnetically separated by a recovery apparatus mounted on a recovery ship. The magnetic body is provided with heightened affinity for the heavy oil by coating surface of a fine magnetite particle with a hydrophobic coating of stearic acid. The magnetic attractive force of the recovery apparatus to the magnetite affects the heavy oil through the stearic acid, and sea water and the heavy oil are efficiently separated by magnetic force.
Fujieda et al., U.S. Patent Application Publication 2010/0059448 discusses a water treatment composition and method of using it to treat water containing pollutants. The composition comprises magnetic particles, which include magnetic powder subjected to surface treatment with a particular organometallic compound. The composition can be rapidly separated by a magnetic force. The organometallic compound comprises a metal atom connected to an alkoxy group and an amphipathic organic group. The magnetic substance may be a material exhibiting ferromagnetism at room temperature, such as any ferromagnetic material, e.g., iron, iron alloy, magnetite and others. The sizes and shapes of the magnetic particles can be controlled, and the mean size is preferably 0.2 micrometer to 5 millimeters. The magnetic powder may comprise magnetic granules having surfaces subjected to hydrophobic treatment with alkoxysilane compounds, e.g., methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane and phenyltriethoxysilane. The water treatment composition, is used in a water treatment method to remove pollutants, such as organic pollutants or particularly oils, e.g., mineral oils, animal and vegetable fats and oils, hydrocarbons and aromatic oils.
Murai et al., US Patent Application Publication US 2009/0321363 discusses particles and a method for treating water with the particles similar to that of Fujieda. After the surfaces of the magnetic particles are treated with silane coupling agents containing amino groups, the amino groups are reacted with halogenated hydrocarbons having hydrocarbon chains (i.e., hydrophobic moieties). Normally, the mean size of the magnetic particles is 0.1 to 1000 μm.
Bradbury, et al., U.S. Pat. No. 5,397,476, discusses a method for removing pollutant ions from an aqueous solution, which comprises contacting the solution with particles of a composite magnetic resin which includes magnetic particles embedded in an organic polymeric matrix. The organic polymeric matrix either contains or has attached to it sites which are selective for the pollutant ions in the presence of other ions, which are not desired to be removed. In the next step, composite magnetic resin particles are separated by magnetic filtration from the solution. Then, the separated composite magnetic resin particles are subjected to regeneration using an appropriate regenerant solution, and are separated from the regenerant solution and recycled.
Etemad et al., US Patent Application Publication 2010-0051557 discusses a process for eliminating heavy metal cations from an aqueous medium. The process comprises two stages: in the first stage, iron oxide nanoparticles, such as magnetite, are suspended in an aqueous medium contaminated with the heavy metal cations, and in the second stage the solution is brought into contact with a ferromagnetic matrix (or a paramagnetic matrix) magnetized by an outside magnetic field. The heavy metal cations are deposited on the matrix under the imposed magnetic field and then separated from the matrix. The heavy metal cations are cadmium, lead and copper.
Prenger et al., U.S. Pat. No. 6,596,182 discusses a process for removing heavy metals from water which includes the steps of introducing magnetite to a quantity of water containing heavy metal and mixing the magnetite with water, so at least a portion of the heavy metal is bound to the magnetite. The magnetite and the absorbed metal are removed from the water by application of a magnetic field, e.g. by flowing the water through a solid magnetized matrix, such as a steel wool, so that the magnetite magnetically binds to the solid matrix. Alternatively, the magnetized matrix is subject to an externally applied magnetic field. Once the magnetite and the heavy metal is bound to the matrix, it can be removed and disposed of. The magnetite may be formed in situ.
Rampersaud et al., US Patent Application Publication US 2010/0012880, discusses particles which may have a magnetic particle having a protective layer and a hydrophilic and a hydrophobic portion.
However, a need still exists in the art to overcome deficiencies and limitations of previously-existing methods.